If you click on "deactivate" in the OSS menue, you will be asked which operating system you want as standard. If you chosse Win XP, your SuSE bootmenu will be lost (but you can repair it with the installtion procedure from SuSE). If you chosse SuSE as standard, you will get to the SuSE bootmenu during the boot process and will be able to chosse Win XP or SuSE Linux to start.